Susan Glaspell’s play operates successfully on several levels, so an effective thesis statement will depend on identifying one significant aspect on which to build. The play is a mystery insofar as the policemen and the women try to determine if Minnie Wright killed her husband, John, and if so, why she did it. Going a bit deeper, one can examine it as a psychological drama that addresses multiple family dynamics that finally culminated in extreme violence. A thesis statement related to this type of analysis would center on Minnie Wright and make an assertion about her motivations for homicide, such as: Because John pushed her too far when he killed the bird, Minnie snapped and murdered her husband.
One interesting thing Glaspell does, however, is to keep both the apparent protagonist and antagonist offstage. The audience meets neither the wife nor the husband. Mrs. Hale and Mrs. Peters, who are helping their neighbor, occupy the stage. In that regard, another line of analysis would focus on them—both their relationship to each other and to the policemen with whose views they disagree. Are these two female characters interchangeable? If not, how do they differ? A relevant thesis could relate to the greater importance of one of them. For example, in concealing the canary, Mrs. Hale deliberately obstructs the investigation because she wants to protect her old friend.